8 octahedrons spinel 7.5 four-sided prisms zircon 7 hexagonal prisms smoky quartz 7 three-sided prisms tourmaline 7 non-crystalline flint 6 non-crystalline opal 5.5 short eight-sided prisms pyroxene 5.5 long six-sided prisms amphibole 2-3 cleaves into thin sheets mica Black 9 hexagonal prisms corundum 8 octahedrons spinel 7 three-sided prisms tourmaline 5.5 short eight-sided prisms pyroxene 5.5 long six-sided prisms amphibole 2-3 cleaves in thin sheets mica The Gold Group Gold was undoubtedly the first metal to be used by primitive man; for, occurring as it did in the stream beds, its bright color quickly attracted the eye, and it was so soft, that it was easily worked into various shapes, which, because they did not tarnish, became permanent ornaments. The metal is associated with the very earliest civilizations, being found in such ancient tombs as those at Kertsch in Crimea and in northern Africa and Asia Minor. It was used in the cloisonné work of Egypt 3000 years B.C. In America the Indians, especially to the south, were using it long before the continent was discovered. Of all the metals gold is the most malleable, and its ductility is remarkable, for a piece of a grain’s weight (less than the size of a pin head) can be drawn out into a wire 500 feet long; and it can be beaten into a thin leaf as thin as ¹/₂₅₀₀₀₀ of an inch in thickness, and thus a bit, weighing only a grain, can thus be spread over 56 square inches.